CVE-2026-31694 fuse: reject oversized dirents in page cache

High 7.8 Published 1 May 2026 Updated 15 Oct 2026

A malicious FUSE server can trigger a kernel buffer overflow via oversized directory entries, potentially leading to code execution or privilege escalation.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2026-31694?

CVE-2026-31694 is a high-severity memory corruption vulnerability in Linux kernel, published on 1 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

fuse: reject oversized dirents in page cache

fuse_add_dirent_to_cache() computes a serialized dirent size from the server-controlled namelen field and copies the dirent into a single page-cache page. The existing logic only checks whether the dirent fits in the remaining space of the current page and advances to a fresh page if not. It never checks whether the dirent itself exceeds PAGE_SIZE.

As a result, a malicious FUSE server can return a dirent with namelen=4095, producing a serialized record size of 4120 bytes. On 4 KiB page systems this causes memcpy() to overflow the cache page by 24 bytes into the following kernel page.

Reject dirents that cannot fit in a single page before copying them into the readdir cache.

Which versions are affected by CVE-2026-31694?

It affects 2 products.

Products include Linux kernel, Siemens Simatic S7-1500 Tm Mfp Firmware.

How do I fix CVE-2026-31694?

Apply the vendor's patch.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2026-31694 being exploited?

There is no known exploitation of CVE-2026-31694 in the wild and no public exploit code.

Public exploit code: 1 proofs of concept on GitHub.

All Linux kernel vulnerabilities

Sources

Also known as AZL-85424, BELL-CVE-2026-31694, DEBIAN-CVE-2026-31694, GHSA-8fxx-fj7q-42m6, ROOT-OS-DEBIAN-11-CVE-2026-31694, ROOT-OS-DEBIAN-12-CVE-2026-31694 and 3 more.